A toxic waste spill in northern Alberta has killed off roughly 42 hectares of boreal forest, in what could be the biggest environmental disaster in North America in recent history.

The spill was first discovered on June 1st, about 100 kms south of the border with the Northwest Territories, near the small town of Zama City. Texas-based Apache Corporation, the oil company responsible for the spill, just released their estimate of its size on Wednesday. According to their figures, 9.5 million litres of 'produced water' was released into the environment, covering the equivalent of over 50 football fields-worth of land.

"Every plant and tree died," said James Ahnassay, chief of the Dene Tha First Nation, according to The Globe and Mail, as he spoke of the effect the spill has had on the land. The Dene Tha apparently also believe that waterfowl may have been killed in the spill, which took place in a wetlands area, but according to The Globe and Mail, Apache representatives said they saw no impacts on wildlife.

'Produced water' is a toxic combination of salt water, oil and chemicals that's a byproduct of extracting oil from the ground.

Produced water comes from formation fluids which are extracted during oil and gas operations that contain naturally occurring oil, gas, non-potable water, salt and other minerals. As a part of the production process, formation fluids are brought to the surface and treated to remove recoverable oil and gas. The remaining produced water and associated minerals are re-injected back into the producing formation to maintain the integrity of the reservoir. The water release at Zama involved produced water that had already been treated to remove hydrocarbons.

The Energy Resources Conservation Board, Alberta’s energy regulator, said it contained roughly 200 parts per million of oil, or about 2,000 litres in total. But information compiled by the Dene Tha suggests the toxic substance contains hydrocarbons, high levels of salt, sulphurous compounds, metals and naturally occurring radioactive materials, along with chemical solvents and additives used by the oil industry.

So, although this water did have the majority of the useful oil removed, it is far from harmless, and according to the Dene Tha, with the amount of damage the spill has done, it may have been there for months before it was found.

According to The Globe and Mail, the Energy Resources Conservation Board was asked by the Dene Tha to enforce upgrades to the aging equipment and pipelines that companies in the area use, but with this spill Mr. Ahnassay expressed his doubts about the government's efforts: "We don't believe that the government is doing enough to ensure upgrades and maintenance of the lines."

According to Apache, the leak has stopped and the spill has been contained, and they are continuing to map and monitor the affected area as they move equipment and personnel into position to clean up the spill.

In a statement quoted by The Globe and Mail, environmental activist Mike Hudema said: "This latest spill should call into question the provincial government’s decision to hide the pipeline safety report they received last year and the failure to follow through on the public pipeline safety review the Minister of Energy promised last July."